Controllability and Observability - Lecture Notes | ECSE 6400, Study notes of Electrical and Electronics Engineering

Material Type: Notes; Class: SYSTEMS ANALYSIS TECHNIQUES; Subject: Electrical & Comp. Sys. Engr.; University: Rensselaer Polytechnic Institute; Term: Fall 2004;

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13. Controllability
and Observability
Topics
Be ableto
.define and explain the concepts of
complete controllability and complete
observability.
.explain the importance of complete
controllability ana complete observaoility
and relate them to full-state feedback
controllers and observers.
.determine if a discrete-time system is
completelycontrollableand/orcompletely
observable.
Ref: Sections 5.6, 5.7. Fall2004
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13. Controllability

and Observability

Topics

Be able to

. (^) define and explain the concepts of

complete controllability and complete
observability.

. (^) explain the importance of complete controllability ana complete observaoility and relate them to full-state feedback controllers and observers. . (^) determine if a discrete-time system is

completelycontrollableand/or completely
observable.

Ref: Sections 5.6, 5. 7. Fall 2004

General Concepts

In In

I II

C1" I F 2n C2"1^ F

Controllability

. Each loop has a characteristic frequency (or mode) of e -t.

-+

t y

Example

Draw a block diagram for

0 0

0 1 x(t) + lu(t) 1 0

-1 1

y(t) = [1 0 1 0 ]x(t)

Which states are observable? which are

controllable? Which states are part of the transfer function? What is the transfer function?

Complete Controllability (CC)

. all modes are affected by the input

A system is CC iff for every possible x(tI) :3 a u(t), 0 < t < tl 3 the system with zero initial conditions can be forced to x(tI).

Alternate Definitions,

Del

Wh~t does this definition imply about the

Full-State Feedback and Observers

(Recall) What are the benefits of Full-State
Feedback?

Full-state feedback implies that you can measure all of the states.

What if all the states cannot be measured?

Fact: If the system is completely observable,
then you can reconstruct the states from a

knowledge of yet) and u(t).

Controllability Tests for Discrete-Time Systems

Find a control to take the system from an arbitrary x(O)to 0 in k steps.

x(k) = Akx(O)+ Ak-l Bu(O)

  • Ak-2Bu(l) + ...+ Bu(k-l)

Since x(k) is the origin,

Now solve for u(O), u(l), ...

Example

Test this single-input, single-output system for complete observability,

1 0 1 x(k+ 1) = I x(k) + lu(k) -1/2 1/2 -

y(k) = [5 1] x(k) (^) Ans. system is CO

Example

Test this two-input system for Complete Controllability.

.5 .5 0 3 1

x(k+ 1) = 0 1 0 x(k) + 2 0 u(k) .83 -2.16 -.33 -1 1 Ans. system is not CC

Solution

3 1 2.5 .5 2.25.

8=202020c

-1 1 -1.5 .5 -1.75.